Waec Physics 2009 Past Questions and Answers

Question 56:

• WAEC 2009

(a) Explain why it is not advisable to sterilize a clinical thermometer in boiling water at normal atmospheric pressure.
(b) State the effect of an increase in pressure on the
(i) boiling point; and
(ii) melting point of water.
(c) Diagram:

The graph shown above is that of the saturated vapour pressure (s.v.p.) of water against temperature.
Pure water is known to boil at 100\(^o\)C and at an atmospheric pressure of 760 mmHg. What general conclusion can be drawn from the information given above?
d) A thread of mercury of length 20 cm is used to trap some air in a capillary tube with uniform cross-sectional area and closed at one end. With the tube vertical and the open end uppermost, the length of the trapped air column is 15cm. Calculate the length of the air column when the tube is held:
i) horizontally;
ii) vertically with the open end underneath. [Atmospheric pressure = 76 cmHg ]

Question 57:

• WAEC 2009

(a) State two differences between a sound wave and a radio wave.
(b) Explain why a vibrating tuning fork sounds louder when its stem is pressed against a table top than when held in air.
(c)State two conditions necessary for the:

production of stationary wave in a medium;
formation of interference wave patterns;
occurrence of total internal reflection of a wave.

(d) A ray of light is incident on one face of an equilateral glass prism.

Draw a ray diagram to show the path of the ray through the prism.
Calculate the refractive index of the glass if the angle of minimum deviation is 41\(^o\).

Question 58:

• WAEC 2009

(a) State two essential differences between a moving coil galvanometer and a d.c. generator.
(b) Explain the term eddy currents and state two devices in which the currents are applied.
(c) State the principle on which the potentiometer is based when it is functioning.
(d) A source of e.m.f. 110 V and frequency 60Hz is connected to a resistor, an inductor and a capacitor in series. When the current in the capacitor is 2A, the potential differences across the resistor is 80 V and that across the inductor is 40 V. Draw the vector diagram of the potential differences across the inductor, the capacitor and the resistor.
Calculate the:
(i) potential difference across the capacitor;
(ii) capacitance of the capacitor;
(iii) inductance of the inductor. [π = 3.14]

Question 59:

• WAEC 2009

(a) Briefly explain the following terms:
(i) emission line spectra;
(ii) line absorption spectra.
(b) Draw a labeled diagram showing the structure of a simple type of photocell and explain its mode of operation.
(c) State two
(i) reasons to show that x-rays are waves;
(ii) uses of x-rays other than in medicine.
(d) An electron jumps from an energy level of -1.6eV to one of -1.4 eV in an atom. Calculate the energy and wavelength of the emitted radiation. [ h = 6.6 x 10\(^{-34}\) Js; c = 3.00 x 10\(^8\) ms\(^{-1}\); eV = 1.6 x 10\(^{-19}\) J ]

Question 60:

• WAEC 2009

Give three observations in support of de Broglie's assumption that moving particles behave like waves